Process for the electrolytic reduction of organic compounds



Patented Sept. 19, 1933 PATENT OFFICE PROCESS FOR THE ELECTROLYTIC REDUC- TION OF ORGANIC COIVIPOUNDS Lucas P. Kyrides and Johann A. Bertsch, St. Louis, Mo., assignors, by mesne assignments, to Monsanto Chemical Company, a corporation of Delaware No Drawing. Application May 31, 1929 Serial No. 367,614

7 Claims. (Cl. 2049) The present invention relates to improvements in the electrolytic reduction of unsaturated organic acids or salts thereof, according to which a novel electrolytic medium is employed in effecting the reduction.

, The invention likewise contemplates the provi sion of a process for efi'ecting reduction of organic compounds in which the resistance to reduction is lowered, the volatile disagreeable 10 fumes are obviated, the danger in handling the electrolytic medium is minimized, the oxidation of the electrolytic medium is avoided and the cost of recovering the product from the electrolyte is reduced.

These together with other advantages of the process will become apparent from a description of a specific application of the principles underlying the same.

Example A lead lined container is filled partly with a three and one-half percent aqueous benzene sulfonic acid solution. An electrode, which preferably has previously been coated with peroxide, is employed as a cathode. A graphite, magnetite. or preferably a chromium-nickel steel electrode is employed as an anode. Such electrodes may be separated by means of one or more porous diaphragms.

Sufllcient maleic acids and/or fumaric acid are dissolved in the electrolytic medium to form a 10% to solution or dispersion of the acid body, after which the reduction is allowed to proceed using a current density of from 2 to 5 amperes per square decimeter of cathode surface. In order to overcome the varying acid concentration caused by migration of the sulfonic acid anolyte is withdrawn from time to time, concentrated, and returned to the catholyte. As the reduction proceeds the current density may advantageously be reduced. The temperatures of the electrolyte require no special regulation, since it appears to have but slight eifect upon the efficiency and yield of the unit. If desired the acid body may be supplied and the succinic acid removed continuously. The product which is present in the cathode liquors is separated by crystallization, is white in color and has a melting point of 185 C. Both the yield and the efficiency of the unit are very high.

If desired, the benzene sulfonic acid may be replaced by its homologues or derivatives, such as chlorobenzene sulfonic acid, toluene sulfonic 'acid, disulfonic acid, etc., naphthalene sulfuric acid or homologues or derivatives thereof. Benzene sulfonic acid has been found to give very satisfactory results; after long and repeated use it displays no indication of decomposition, notwithstanding the fact that the literature states that sulfo-acids are completely destroyed by anodic oxidation. Although a lead peroxide cathode and a chromium nickel steel anode have been specified, other suitable materials may be employed, if desired. Similarly a diaphragm compartment has been recommended. This, however, is not to be considered as a limitation of the process. The principles hereinabove set forth are applicable to other organic compositions or monoor poly-carboxylic constitution, their derivatives and salts, such as crotonic acid, 7 cinnamic acid, hydroxy-cinnamic acids, fumaric acid or the normal or acid salts or their anhydrides.

Although there has been described but a single specific example of the applications of the principles of the present invention and the broad application of these principles indicated in a gen eral way, these have been set forth for the purpose of example only and not as limitations. Accordingly it is desired that theinvention be 30. restricted only as required by the prior art and the appended claims.

It has been noted that a lead terminal which has been coated with lead peroxide is an eflicient and satisfactory cathode. In this connection, 35' however, it is to be noted that the stability of the cathode is dependent upon the current flow and that after the flow of current is interrupted the terminal is susceptible to the corroding action of the acid. Under these circumstances it is desirable that a small amount of current flow through the cell as long as the electrode is immersed in the electrolyte.

We claim:

1. The method of electrolytically reducing unsaturated organic acids or salts thereof, which comprises reducing the same in the presence of an aromatic sulfonic acid.

2. The method of electrolytically reducing materials of the class described that comprises reducing the same in the presence of an aqueous solution of a benzene sulfonic acid.-

3. The method of electrolytically reducing unsaturated polycarboxylic organic acids that com- H prises :reducing the same in the presence of an aqueous solution of a benzene sulfonic acid.

4.'The method of electrolytically reducing maleic acid to form succinic acid that comprises electrolyzing an aqueous solution of maleicacirl, containing a quantity of benzene sulfonic acid.

same to electrolytic reduction in thepresence of an aqueous electrolyte containing an aromatic sulfonic acid and under conditions which result in no appreciable decomposition of the electrolyte.

7. The method of reducing maleic acid that comprises subjecting the same to electrolytic reduction in the presence of an aqueous solution of an aromatic sulionic acid.

LUCAS P. KYRIDES. JOHANN A. BERTSCH. 

